1. G protein coupled receptors
generally receptors for slow transmitters
coupled to effector by a G protein
receptors and G proteins found in membranes of cells
large family
many drugs act on these

2. Examples muscarinic ACh receptor adrenoreceptors dopamine receptors
5-HT receptors
opiate receptors
neuropeptide receptors
many have been cloned: similar structure

3. Structure first receptor cloned and sequenced was beta-adrenoceptor
single polypeptide
one subunit forms receptor
amino acid residues long
hydropathy plot
use as before to predict membrane-spanning regions

4. Hydropathy Plot

5. Structure from Hydropathy Plots
7 membrane-spanning regions N C in
out
membrane
Similarity in these membrane regions between the different receptors in this family

6. Rhodopsin much work done on rhodopsin because:
a) it is abundant in retinal rods
b) has a similar structure to these receptors
c) is also coupled to G proteins